In this work two vanadium oxides (V2O5 and VO2) were prepared by green synthesis method using ammonium vanadate (NH4VO3) and extract of orange peel. V2O5 and VO2 have various applications in lithium-ion battery, sensors, transistors, photo catalysis, supercapacitors and electrochromic devices. The effect of calcination atmosphere is obvious as calcination the precursor of (NH4VO3) and extract of orange peel in air at 450? yielded V2O5 while calcination in vacuum at the same temperature gave the reduced form VO2 as estimated by X-ray powder diffraction (XRD). These two different phases of vanadium oxides have different morphologies. Investigation by transmission electron microscope revealed that V2O5 oxide which synthesized in air at 450? showed big particles with laminar shape. The particles look arranged layer over layer with sizes exceed 200 nm. While images of VO2 prepared in vacuum at the same temperature showed different shape and size for their particles. The neutral atmosphere provided by vacuum not only gives reduced form of vanadium oxide (VO2) but also minimizes and changes their particles size and shape, respectively. Unidentified shape of nano sized particles were observed for this reduced oxide. These particles have sizes less than 100 nm and much lower than those observed for V2O5 particles.
